Marking foam system for agricultural equipment

ABSTRACT

A marking system for indicating the boundaries of an area that has been treated includes a storage tank for storing the liquid and the foaming agent that is fluidically separated from a foam tube. A mixing control element fluidically connects a compressor to the foam tube and connects the storage tank to the foam tube whereby the ratios and parameters associated with the formation of the marking foam can be varied. The system includes two marking foam dispensing nozzles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to land vehicles, and inparticular to agricultural vehicles and systems associated with suchagricultural vehicles. Specifically, the present invention relates to amarking system for indicating the boundaries of an area treated by anagricultural vehicle.

2. Description of the Prior Art

Modern agricultural science includes the treatment of large areas formany reasons, such as applying fertilizers, herbicides, insecticides andthe like. For many reasons, including economy, ecology, efficiency andmaximized coverage, it is important that the area being treated beclearly marked to distinguish the areas that have already been treatedfrom the areas that have not yet been treated.

For this reason, there have been several proposals for systems thatdemark and identify areas of treatment by various agriculturaltechniques and processes. Some of these proposals have includedmechanical demarcation devices, and some of the proposals have includedspraying marking foam to form the marking system.

No matter what design is used, however, there are certain requirementsthat should be met to ensure that the marking system is effective forthe intended purpose.

For example, the marking system should be amenable to efficientoperation by a minimum number of people. It is this requirement thatoften presents drawbacks to the mechanical systems.

Still further, the marking system should not, itself, be a source ofcrop damage. Here, also, the mechanical systems have been found lacking.

The agricultural marking system will be subject to many conditions thatmay change within a single operation and may also change from operationto operation. In order to be most effective, the marking system shouldbe amenable to producing a clear marking system under all sorts ofconditions which may be subject to change even within a singleapplication.

While mechanical systems involving placement of stakes or the like maybe somewhat amenable to providing a clear marking system each time, suchsystems are so wasteful of manpower and may be so time consuming as tomake them economically undesirable. Coupled with the other disadvantagesof such systems, mechanical marking systems do not appear to be a viableway of effecting the marking of areas of treatment.

In view of the shortcomings of mechanical systems, there have beenseveral proposals for nonmechanical marking systems. These nonmechanicalsystems generally involve the use of marking foam that is sprayed ontothe area behind a motor vehicle.

While somewhat effective in overcoming the just-mentioned drawbacksasscociated with mechanical marking systems, the present foam sprayingsystems have their own drawbacks.

Chief among such drawbacks results from the lack of adaptability forthese systems. That is, the marking systems that spray foam onto an areato demark that area are subject to producing results of varyingeffectiveness as conditions change.

For example, as discussed above, it is necessary for the marking systemto provide a clearly evident mark over the entire range of the areabeing treated. This mark should not deteriorate to a level that itcannot be easily seen by workers at a later time whereby analready-treated area is re-treated because the markings were not evidentenough. Clearly, to ensure such a situation does not exist, the markingfoam can be made dark and thick enough to compensate for such a laterdeterioration of marking foam. However, such a solution may provewasteful of marking foam by making some areas too dark in order toensure that other areas have marks that are dark enough to be easilyseen. This problem of nonevident markings may also occur at or near theend of a run when the supply of marking foam-producing material isnearly exhausted.

Another problem associated with the lack of adaptability of present foammarking systems occurs when conditions of a run change from earlierconditions within that run or from conditions existing in a prior run.System settings may make the marking acceptable for the earlier-existingconditions, but not for the later-encountered conditions. This can alsobe a result of portions of the dispensing system functioning differentlyat different times, for example due to clogging or the like. Presentsystems really do not have any effective method for accounting for suchvariation in operating conditions, and thus, nonuniform markings mayresult from the present systems which mark using foam which is appliedusing a spray system.

Still further, in order to be most effective, that portion of theoverall system directed to fluid storage should be designed specificallyfor fluid storage, and that portion of the overall system directed tomarking foam production should be designed for such operation. However,in most of the present systems, one tank is used to both store and makethe marking foam. This requires such a tank to balance designconsiderations whereby some storagerelated functions may be lessefficient in order to make foam-making functions viable and vice versa.System maintenance and cleaning may be difficult in such systems aswell.

Since the final foam-marking product may be dependent on the ratio ofthe various components used to form that marking foam and the conditionsunder which it is formed, to be most effective, the overall systemshould include some means for controlling and varying such parameters asnecessary. However, present systems generally make the marking foam in asingle tank and then dispense that foam using nozzles or the like. Thereis no means for varying the conditions or the ratios, or both,associated with the making and the dispensing of the final foam-markingproduct. Therefore, the final product in most of the present systems maynot have the proper quality to be most effective for a particularapplication.

A still further drawback to present systems is the use of a pump formoving foam through the system. It may be more efficient to move liquidor a mixture of liquid and foaming agent by some means, and then to movemarking foam using a motive means that is most efficient in moving suchfluids. Present marking foam systems do not make this distinction influid properties and thus, may not be efficient as possible.

Therefore, while present marking systems that use marking foam aresuccessful in overcoming some drawbacks associated with other systems,the nonadaptability and lack of efficient foam-forming and moving meansof such foam marking systems may create problems that tend to vitiatethe overall performance of such systems.

Accordingly, there is a need for marking system that uses marking foam,but which is adaptable and amenable to changing operation to account forchanging conditions to produce effective markings for all conditions towhich the system may be exposed, and which can be designed to be mostefficient in its overall operation.

OBJECTS OF THE INVENTION

It is a main object of the present invention to provide a foam markingsystem for indicating the boundaries of an area treated by anagricultural vehicle that is capable of providing efficient andeffective markings under all conditions.

It is another object of the present invention to provide a foam markingsystem for indicating the boundaries of an area treated by anagricultural vehicle that is capable of varying the parameters affectingthe makeup of the foam dispensed during the operation of the system in amanner that produces the most effective markings for a particularapplication.

It is another object of the present invention to provide a foam markingsystem for indicating the boundaries of an area treated by anagricultural vehicle that has the components thereof capable of beingdesigned for the most efficient operation associated with thatparticular element.

It is a specific object of the present invention to provide a foammarking system for indicating the boundaries of an area treated by anagricultural vehicle that has the foam-making product storage elementseparated from and independent of the foam makeup and foam-formingelements.

It is another specific object of the present invention to provide a foammarking system for indicating the boundaries of an area treated by anagricultural vehicle that includes a specific element that can becontrolled to produce marking foam that is most effective for aparticular application and condition.

SUMMARY OF THE INVENTION

These and other objects are achieved by a foam marking system which isadapted for use with agricultural vehicles to indicate the boundaries oftreated areas, which system includes means for quickly and easilyvarying the parameters and ratios of the components of the marking foambeing dispensed. The system fluidically and physically separates thefoam-making elements from the storage elements, and thus, permitsvariation of the various parameters without unduly affecting the otherparameters.

In this manner, the marking system can be adjusted to account forchanged conditions to produce the most effective and efficient marking.This change can be effected between runs or during a run if necessary.Still further, due to this separation of elements, each element can bedesigned to accomplish the objectives associated therewith withoutsacrificing other objectives and design factors associated with otherfunctions of the system. This separation of elements also permits use ofpumping devices that are designed for the most efficient operation ofthe system and are not constrained in the manner of many prior artsystems.

Specifically, the foam spray marking system embodying the presentinvention includes an air compressor and a storage tank that is adaptedto store liquid and a foaming agent and which is fluidically connectedto the air compressor. The system also includes a mixing control meanswhich is fluidically connected to the air compressor and to the storagetank and has means for mixing the compressed air with the mixture ofliquid and foaming agent dispensed from the storage tank to form amixture that is usable for generating marking foam. This mixing controlmeans is fluidically coupled to a foam tube which converts the fluidfrom the mixing control means into marking foam.

The mixing control means includes means that can adjust the amount ofcompressed air being used to form the marking foam fluid and the amountof liquid/foaming agent being used in such fluid independently of eachother whereby the most efficient and effective marking foam can begenerated in the foam tube for the particular conditions to which theoverall system is subjected at any particular time during its operation.

The adjustment means includes a solenoid-operated valve or aventuri-like fluid mixing chamber wherein compressed air flows past adispensing spray nozzle to assist in the withdrawing of liquid/foamingagent therefrom. The amount of fluid and the mixing ratios involved canthus be readily adjusted to meet the exact conditions of the system atany time.

Further control of the system can be effected since the system includescontrol valves and the like which are situated in the system to effectthe most desirable control over the fluid flowing in the system. The aircompressor is used to drive the liquid mixture out of the storage tank,and thus, the system embodying the present invention does not requirepumps for moving foam, and the amount of compressed air flowing to thestorage tank can be adjusted to account for supply depletion in thatstorage tank without adversely affecting the ratios and parametersassociated with the making of the marking foam in the foam tube. Thismakes the overall system more efficient and reliable than many prior artsystems that rely on pumps to move fluid from one place in the system toanother.

The physical and fluidic separation of the various components of thesystem also permit each component to carry out its intended function inthe most effective and efficient manner, and also permits the system tobe easily and efficiently serviced while also permitting the system tobe modified to account for vagaries in the operation of individualcomponents, such as might result from the malfunctioning of one markingfoam dispensing nozzle.

Other objects and advantages of this invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the overall system embodying thepresent invention mounted on an agricultural vehicle.

FIG. 2 is a schematic showing the fluid circuit associated with the foammarking system embodying the present invention.

FIG. 3 is a perspective view showing the check valve used in the systemembodying the present invention.

FIG. 4 is a side elevational view showing a foam tube and mixing controlmeans used in the system of the present invention.

FIG. 5 is a side elevational view of an alternative form of the mixingcontrol means used in the system embodying the present invention.

FIG. 6 is a perspective view showing a three-way control valve used inthe system of the present invention.

FIG. 7 is a side elevational view, partially cut away, showing a markingfoam dispensing nozzle used in the system of the present invention.

FIG. 8 is a schematic showing the fluid circuit associated with a foammarking system comprising a first modified embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

Shown in FIG. 1 is an agricultural vehicle 10, such as a tractor or thelike, which is used in treating areas with fertilizers, herbicides,insecticides or the like. The vehicle 10 therefore includes a dispersingsystem 12 which is used in the dispersing process. Neither theparticular dispersing system nor the particular agricultural vehicleform a part of the present invention, and will thus not be discussed ingreater detail. However, it is noted that the dispersing system willinclude the elements usual to such systems, such as appropriatedispersing nozzles or the like which are located with respect to thevehicle to disperse the material of interest in the most efficientmanner.

As discussed above, it is important to mark the boundaries of the areastreated, and thus, the vehicle 10 includes a spray marking system 14which is the subject of the present invention.

As shown in FIG. 1, the marking system 14 includes a sprayer boom 16mounted on the vehicle 10, and which includes a plurality of sectionsthat are adjustably coupled together at joints 18. The sprayer boom 16includes an upper arm 20 and a lower arm 22 adjustably attached to thevehicle and each section includes an upper arm, such as upper arm 24 ofoutermost section 26, and a lower arm, such as lower arm 28 of outermostsection 26, which are adjustably connected to the corresponding arms ofthe next section by the joint 18.

Movement of the sprayer boom 16 with respect to the vehicle 10 iscontrolled by the vehicle operator, and the means for moving such boomcan include motors, controls located to be within easy reach of avehicle operator sitting in the cab C of the vehicle and the like, aswell as suitable joints and the like. The manner of moving the sprayerboom 16 with respect to the vehicle 10 will occur to those skilled inthe art based on the present disclosure, and thus will not be furtherdiscussed.

As shown in FIG. 1, the sprayer boom 16 includes a marking foamdispensing nozzle 30 on one end thereof, and a second marking foamdispensing nozzle 32 on the other end of the boom. The dispensingnozzles 30 and 32 are located to dispense marking foam onto the groundat the outer boundaries of the area treated by the dispensing system 12,and are supplied with marking foam by the system 14 in the mannerdiscussed below. The nozzles 30 and 32 are angled and oriented todispense marking foam in the most visible manner, and will also bediscussed in greater detail below with regard to FIG. 6.

Referring next to FIG. 2, the marking system 14 forming the subject ofthe present invention will be discussed. As shown in FIG. 2, the markingsystem 14 includes a compressor means 40 which is adapted to drawambient air thereinto, compress such air to a desired degree, and forcesuch compressed air out through an outlet line 42. The compressor means40 can include the usual elements, and is driven by a power source, suchas a battery pack 44 or the electrical system of the agriculturalvehicle 10, and is controlled by means of an on/off switch 48. Thedegree of compression of the air in the outlet line 42 can be controlledby a pressure regulator 46 to control the pressure of the compressed airbeing supplied to the remainder of the system by the compressor means 40for purposes of controlling the quality and quantity of the marking foamdispensed by the system 14, as will be evident from the discussionpresented below.

Compressed air in line 42 flows through the pressure regulator 46 to ajunction means or tank T-coupling 50 which is fluidically connected to astorage tank 52. The junction means 50 includes a pressure gauge 51which is shown as being mounted on the junction means 50, but can bemounted in the vehicle cab C. The gauge 51 provides a visual readout ofthe pressure of the compressed air being supplied by the compressormeans 40 so that system 12 parameters can be set to the most desirablevalues. The junction means 50 will be further discussed below in regardto FIG. 3. The storage tank 52 is adapted to contain liquid, such aswater, and foaming agent, such as is commonly used in field marking, andhas an inlet 54 to which a first outlet 56 of the junction means 50 isfluidically connected to flow compressed air into the storage tank in amanner that may be controlled by a check valve means 55 to pressurizethe fluid in the storage tank to a level great enough to providesufficient motive force to drive the fluid through the remainder of thesystem as will be seen from the ensuing discussion. The storage tankalso has an outlet 58 through which a liquid/foaming agent mixture flowsto be used by the remainder of the marking system 14.

The liquid/foaming agent mixture from storage tank 52 flows via conduit60 to a mixing control means 70, which will be further discussed below,and is mixed with compressed air exiting the check valve means 55 whichmay be located in a second outlet 72 of the junction means 50 andflowing in conduit 74 therefrom to the mixing control means 70.

The mixing control means 70 combines compressed air from conduit 74 witha liquid/foaming agent mixture from conduit 60 in a ratio and in amanner as set by the components of the marking system 14 to form amarking foam-forming mixture. The mixing control means 70 is fluidicallyconnected to an inlet 76 of a foam tube 78 to conduct this markingfoam-forming mixture into the foam tube 78. This marking foam-formingmixture is converted into marking foam in the foam tube 78 and exitsthat foam tube 78 via an outlet 80.

A conduit 82 fluidically connects the foam tube outlet 80 to an inlet 81of a selecting means 84 which further includes a first outlet 86fluidically connected to a conduit 88 for fluidically connecting foamdispensing nozzle 30 to the foam tube 78 to receive marking foamtherefrom, and a second outlet 90 for fluidically connecting secondmarking dispensing nozzle 32 to the selecting means 84 via conduit 92whereby, when the selecting means 84 is appropriately operated, markingfoam from the foam tube 78 is dispensed to the dispensing nozzle 32.

Operation of the selecting means 84 is controlled to select nozzle 30unless a special command is given. This operation is preferably carriedout by including a spring biasing means in the selecting means 84 tobias the outlet 86 into fluid connection with the inlet 81 of theselecting means 84, and to further include an electromagnetic device toovercome this spring bias when energized to move the selecting means 84to fluidically connect the outlet 90 to the selecting means inlet 81.Such electromagnetic device can include an electromagnet in theselecting means 84 connected by a line 91 to a switch 93 that isconnected to the battery pack 44. Operation of the switch 92 energizesthe electromagnet to move the second outlet 90 into fluid connectionwith the inlet 81; whereas, unless the electromagnet is energized, theselecting means 84 will be spring-biased into a configuration thatfluidically connects the first outlet 86 to the inlet 81. In thismanner, the system can mark an area using either dispensing nozzle 30 ordispensing nozzle 32 as selected by the operator.

Operation of the marking system 14 is as follows: ambient air iscompressed to a selected pressure by the compressor means 40 and flowsto the storage tank 52 via the conduit 42, the pressure regulator 46 andthe junction means 50 to pressurize the fluid contained in that storagetank. This pressurized fluid is then forced out of the storage tank intoconduit 60 as a liquid/foaming agent mixture and moves to the mixingcontrol means 70 to be combined with compressed air from the check valvemeans 55 and conduit 74. The ratios and parameters of the mixing of thecompressed air from conduit 74 and the liquid/foaming agent from conduit60 are varied and controlled by the mixing control means 70 to form astarting material for use in the foam tube 78 to generate the markingfoam MF that is most desirable for a particular application.

As discussed above, the conditions to which the system 14 is exposed mayvary from run to run or even within an individual run, and thus, theability of the system 14 to vary the parameters and ratios of themarking foam-generating mixture permits the system to account for suchchanges in conditions.

Having discussed the overall system 14 and its operation, attention isnext directed to FIGS. 3-7 for a discussion of the individual elementsof that system.

Referring to FIG. 3, the junction means or tank T-coupling 50 is shownas having a coupling flange means 96 for releasably coupling thejunction means 50 to the storage tank 52. This coupling means 96 caninclude hand-operated cams or the like. As is also shown in FIG. 3,second outlet 72 of the junction means 50 is fluidically connected to avalve assembly 98 including a valve T-coupling 99 with an inlet 100fluidically connected to the junction second outlet 72. The valveT-coupling 99 includes a primary outlet 101 and a secondary outlet 102.The primary outlet 101 is connected to the compressed air conduits 74via a nipple 103. The check valve means 55 selectively controls the flowof air from the primary outlet 101 to the air conduit 74. The nipple 103and the check valve means 55 may be secured in place on the primaryoutlet 101 by a wing nut 104.

The check valve means 55 can be adapted for delayed opening when apredetermined pressure level is attained in the storage tank 52, forexample, five pounds per square inch (psi). By delaying the opening ofthe check valve means 55 and the introduction of compressed air throughcompressed air conduit 74 into the foam tube 78, the markingfoam-forming mixture from the conduit 60 can accumulate in sufficientquantities in the mixing control means 70 to form marking foam MF havingthe desired properties. Furthermore, the check valve means 55 maycontrol the air pressure in compressed air conduit 74 with respect tothe pressure in the storage tank 52, which determines the pressure inthe marking foam-forming mixture conduit 60. For example, in operationthe air pressure in the air conduit 74 may be in the range of nine tofifteen pounds per square inch, and the pressure in the storage tank 52may be in the range of fifteen to thirty pounds per square inch, withthe pressure differential being established by the check valve means 55.As alternatives to the check valve means 55, various other flow andpressure regulating devices could be employed in the valve T-coupling 99or the compressed air conduit 74.

The secondary outlet 102 mounts a bleeder valve 106 with an openposition for communicating the tank 52 with the atmosphere and a closedposition. With the marking system 14 in operation, the bleeder valve 106is normally closed. The bleeder valve 106 is used to bleed compressedair from the marking system 14, and in particular from the storage tank52. The bleeder valve 106 may be opened before the coupling 96 isremoved from the storage tank inlet 54 to prevent the coupling 96 andthe various components attached thereto from being hurled off of thestorage tank 52 by the force of the compressed air therein.

It is also noted that the pressure gauge 51 can include a remotelylocated signaling device and/or feedback control system for furtheradjusting and controlling the operation of the system 14. The checkvalve means 55 can also include means for automatically opening when thepressure reaches a predetermined level, such as five psi, seven psi, tenpsi, or the like.

Referring next to FIG. 4, the preferred form of the mixing control means70 is shown to include a solenoidoperated valve 110 fluidicallyinterposed in the conduit 60 between the storage tank 52 and the foamtube 78. The solenoid valve 110 is powered via line 112 connected to theon/off switch 48 to control the flow of fluid in the line 60. Bysuitably controlling the opening and closing of the solenoid valve 110,more or less liquid/foaming agent mixture may be supplied for producingthe marking foam starting agent.

A filter 118 may be fluidically interposed between the conduit 60 andthe solenoid operated valve 110, and a hand adjusting means 120 can alsobe included to permit easy dismantling of the mixing control means 70for purposes of cleaning or the like.

Located downstream of the solenoid valve 110 is a mixing T-coupling 122having a body 124 adapted to form a mixing chamber 126 and a first inletmeans 128 adapted for cooperable coupling with the solenoid valve 110 bymeans of suitable coupling means, such as nipples, nuts and the like, tofluidically couple the chamber 126 with the storage tank 52 to receiveliquid/foaming agent mixture therefrom. The mixing T-coupling 122 alsoincludes a second inlet means 130 adapted to be releasably coupled tothe compressed air conduit 74 to fluidically connect the chamber 126 tothe compressor means to receive compressed air therefrom.

The mixing control means 70 further includes a spray nozzle means 134fluidically coupled to the conduit 60 to dispense liquid/foaming agentin a spray pattern in the chamber 126. The spray pattern is indicated inFIG. 4 by the reference indicator S and is directed inwardly of thechamber 126. The spray nozzle means 134 can be of any design which issuitable for producing the fan spray pattern indicated in FIG. 4. Theorifices of the spray nozzle means 134 affect its spray pattern S, andspray nozzle means having various numbers, sizes and configurations oforifices can be chosen to provide desired spray patterns of theliquid/foaming agent. Compressed air from conduit 74 is directed intothe chamber 126 in the direction indicated by arrow A in FIG. 4, to flowtowards the outlet 136 and is located and adapted to cooperate with theflow of the spray to combine the compressed air with the fluid in thespray within the chamber 126. This combination produces a mixture thatflows to the foam tube 78 to be converted into marking foam in that foamtube 78. For this reason, the mixture formed in the chamber 126 will bereferred to as marking foam starting mixture.

The foam tube 78 includes means for converting the marking foam startingmixture into marking foam MF, and such means can include steel wool W,Teflon scouring pad material or the like, and various foraminous screensand layers of material M.

As can be seen from the above, the quality and quantity of marking foamMF generated by the foam tube 78 can be controlled by adjusting the flowof compressed air into the chamber 126, by adjusting the flow ofliquid/foaming agent mixture via the solenoid valve 110, or by adjustingthe foam tube 78 itself. In this manner, the overall marking foam MF canbe adjusted as necessary. It is also noted that the flow of compressedair across the spray nozzle 134 affects the amount of fluid dispensedfrom that nozzle, and the quality and quantity of marking foam MFproduced can also be altered and controlled by means of the speed andamount of compressed air flowing across the spray nozzle 134 in a manneranalogous to the conditions existing in a carburetor. In fact, toemphasize this feature of the system, attention is directed to FIG. 5which shows the carburetor situation. It is noted that the operation ofthe FIG. 5 element is so similar to that of a carburetor that the fulldiscussion of carburetor action will not be presented, but reference ismade to standard texts, such as "The Internal Combustion Engine" byCharles F. Taylor and published by the MIT Press, for a full discussionof such action. It is noted that such discussion of the Taylor book isincorporated herein by reference thereto. Thus, as indicated in FIG. 5,the spray nozzle 134 is replaced by dispensing conduit 138 locatedadjacent to the throat area of a venturi-shaped passage 140, andcompressed air from conduit 74 flows through the passage 140 and pastconduit 138 to assist in the dispensing of fluid from that conduit. Thecompressed air mixes with the fluid from the conduit 138 and forms themarking foam starting mixture in chamber 142 that then flows to the foamtube 78 as indicated in FIG. 5 by arrow F.

Referring next to FIG. 6, the selecting means 84 is shown in detail. Itis noted that this element is fully discussed in U.S. Pat. No.3,985,333, assigned to Spraying Systems Co. of Wheaton, Ill., and thedisclosure thereof is fully incorporated herein by reference. Theselecting means 84 is described by the assignee as being "AA144-1-3Three-Way Solenoid-Operated Directovalve". When power is applied to theselecting means 84, marking foam MF is directed to conduit 88 and flowto conduit 92 stops; whereas, when power is off, marking foam flows toconduit 92 and stops flowing to conduit 88. A cap 144 closes off oneconduit of the selecting means.

The marking foam dispensing nozzles 30, 32 are identical, and nozzle 32is shown in FIG. 7. The marking foam dispensing nozzles 30, 32 eachincludes a right-angle coupling 146 for connection by a hose clamp 149to a respective conduit 88 or 92. A flexible connector tube 147 has aproximate end 148 connected to the coupling 146 by a hose clamp 149, andalso has a distal end 150. A nozzle skirt 151 includes a neck 152connected to the connector tube distal end 150 by a hose clamp 149 and abottom 153 open to an interior 154. The skirt neck 152 extends into theskirt interior 154 and mounts a foam screen 155 by means of a hose clamp149. The foam screen 155 may comprise, for example, open-wovenfiberglass cloth or mesh formed as a porous, closed-end tube. The foamscreen 155 functions to capture foam as it is dispensed under pressurefrom a conduit 88 or 92, and contributes to a certain amount of backpressure through the conduits 88, 92 in the foam tube 78. Such backpressure may be helpful in forming and dispensing the marking foam MF.The marking foam MF is forced through the foam screen 155 and may dropin globules to a field surface for demarcating a boundary of an areatreated by the dispensing system 12. The globules of marking foam MF maydrop at regularly-spaced intervals, or the marking foam MF may bedispensed substantially continuously. However, spaced globules aregenerally sufficient in the field to demarcate a boundary of an areatreated by the dispensing system 12.

A foam marking system 160 comprising a first modified embodiment of thepresent invention is shown in FIG. 8 and includes a pump 162 incommunication with the liquid foaming agent conduit 60 for pumpingliquid foaming agent from the storage tank 52 to the mixing controlmeans 70. Pressurized air is communicated from the compressor 40 via thecompressor outlet line 42 to a check valve 164 and thence via thecompressed air conduit 74 to the mixing control means 70. The foammarking system 160 operates to produce marking foam MF in a mannersubstantially similar to the marking system 14, except that with thesystem 160 liquid foaming agent is pumped from the storage tank 52 tothe mixing control means 70 and pressurized air is communicated from thecompressor 40 to a check valve 164 and then to the mixing control means70.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. A field spray marking system for indicating the boundariesof an area treated by an agricultural vehicle comprising:(a) acompressor means for supplying compressed air; (b) a storage tank beingadapted to store liquid and foaming agent therein for forming aliquid/foaming agent mixture and having an outlet through which saidliquid/foaming agent mixture exits from said storage tanks; (c) pumpmeans connected to said storage tank outlet for pumping saidliquid/foaming agent mixture therefrom; (d) mixing control meansincluding a chamber fluidically connected to said compressor means toreceive compressed air therefrom and fluidically connected to said pumpmeans to receive liquid/foaming agent mixture therefrom, said mixingcontrol means including means for introducing compressed air to thechamber, said mixing control means including means for spraying saidliquid/foaming agent into said chamber, said mixing control meansincluding means for controlling the mixing of compressed air andliquid/foaming agent; (e) a foam tube having an inlet end with saidmixing control means located thereat, means to produce marking foam, andan outlet end; and (f) a marking foam dispensing nozzle fluidicallyconnected to said foam tube outlet end.
 2. The invention of claim 1wherein said means to produce marking foam comprises a foraminousmaterial in said foam tube.
 3. The invention of claim 2 wherein saidforaminous material is filamentous.
 4. The invention of claim 1 whereinsaid mixing control means includes:(a) a solenoid-operated valve.
 5. Theinvention of claim 1 wherein:(a) said marking foam dispensing nozzlecomprises a first marking foam dispensing nozzle and is selectivelyfluidically connected to said foam tube; (b) a second marking foamdispensing nozzle selectively fluidically connected to said foam tube;and (c) selecting means having an inlet fluidically connected to saidfoam tube outlet end, a first outlet fluidically connected to said firstmarking foam dispensing nozzle, a second outlet fluidically connected tosaid second marking foam dispensing nozzle, a first position fluidicallyconnecting said inlet and said first outlet and a second positionfluidically connecting said inlet and said second outlet.
 6. Theinvention of claim 5 wherein said selecting means comprises:(a) athree-way valve; and (b) solenoid actuation means for moving said valvebetween its first and second positions.
 7. The invention of claim 6,which includes:(a) means for selectively coupling said compressor, saidpump and said solenoid-actuated valve together for simultaneousactuation.
 8. The invention of claim 1 wherein said foam tube isoriented generally vertically with said inlet end thereof comprising alower end and said outlet end thereof comprising an upper end.